Survival of Saccharomyces cerevisiae microencapsulated with complex coacervate after freezing process

Abstract

Complex coacervate from whey protein isolate (WPI)-Saccharomyces cerevisiae (Y) was prepared for microencapsulation by spray-drying. The optimum WPI-Y complex coacervate reached the best interaction for a ratio and pH of 1:13 and 3.28, respectively. The complex coacervate was spray-dried with 10% and 20% w/w of total solids content using maltodextrin DE10 (MD) as wall material and subsequently frozen at 18 C. DSC, FTIR and SEM analyses were carried out to characterize thermal, chemical and structural properties of pure materials and spray-dried WPI-Y complex coacervates. Thermograms of DSC reflected that the spray-dried WPI-Y complex coacervates were better protected when MD concentration increased because the denaturation peak temperature of proteins and enthalpy were higher. These results were confirmed with FTIR analysis since peaks intensity of amino groups was highest in the spraydried WPI-Y complex coacervate containing 20% w/w of total solids content. After the freezing process, reduced decrease in the peaks intensity of the amides in the spray-dried WPI-Y complex coacervate with 20% w/w of total solids content was observed. Morphology of all spray-dried complex coacervates exhibited particles of spherical shapes with concavities, dents and hollows in the center. However, particles after the freezing process displayed fractures in the surface. Finally, yeast survival was higher in the spray-dried WPI-Y complex coacervate with higher concentration of MD and as well after freezing process. Therefore, WPI-Y complex coacervates were stable after freezing process and can be used to stabilize fermentative microorganisms in order to produce frozen dough with similar characteristics that the dough.